Electric welding in car

Submitted: Tuesday, Jun 27, 2006 at 20:16

ThreadID: 35342 Views:6254 Replies:6 FollowUps:10

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Member - Chris R (NSW)

I seem to remember something about destroying car electronics if welding car body without certain precautions. Is this simply about disconnecting the batteries, or is there more?

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Reply By: Truckster (Vic) - Tuesday, Jun 27, 2006 at 20:20

Tuesday, Jun 27, 2006 at 20:20

Pretty much disconnect batteries.

when Awill4x4 off here has done work on mine hes always insisted on that.

AnswerID: 180697

Follow Up By: Wazza - (Vic) - Tuesday, Jun 27, 2006 at 21:23

Tuesday, Jun 27, 2006 at 21:23

Your car has electronics ? :-b

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Follow Up By: Truckster (Vic) - Tuesday, Jun 27, 2006 at 21:48

Tuesday, Jun 27, 2006 at 21:48

and still better than yours :P

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Follow Up By: Member - JohnR (Vic)&Moses - Tuesday, Jun 27, 2006 at 23:53

Tuesday, Jun 27, 2006 at 23:53

enuff to blow Bruce's diodes

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Follow Up By: Member - Chris R (NSW) - Wednesday, Jun 28, 2006 at 20:06

Wednesday, Jun 28, 2006 at 20:06

Wazza a bit off topic - there's not much that's electronic in the troopie either but cripes I had to ask

Thanks Truckster - other advice further on confirms be careful

Chris

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Reply By: Exploder - Tuesday, Jun 27, 2006 at 20:20

Tuesday, Jun 27, 2006 at 20:20

I think you also need to place the Earth lead from the welder as close to the aria that is to be welded as possible.

AnswerID: 180698

Reply By: Member JD- Tuesday, Jun 27, 2006 at 21:20

Tuesday, Jun 27, 2006 at 21:20

Hi Chris,
As you mentioned disconect the batteries,do not hook up the earth to the exhaust as you could pit your big ends bearings if your unlucky,be carefull of combustables..fuel tank..lines.. batt..anything that might lite up and burn...pays to be a little over cautious if there's such a thing..if your doing overheads and your got a full lenght beard protect it...ive burnt chunks out of two of mine over the years.
Hope this helps.
JD

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Follow Up By: Member - Chris R (NSW) - Wednesday, Jun 28, 2006 at 20:10

Wednesday, Jun 28, 2006 at 20:10

Hi JD

Thanks for that you've reminded me to also cover all areas likely to be affected by sparks/heat - including me.

Chris

FollowupID: 437171

Reply By: Kiwi Kia - Wednesday, Jun 28, 2006 at 06:41

Wednesday, Jun 28, 2006 at 06:41

The main problem is the earth return to the welder. The current will always take the path of least resistance so if it has a choice of either going through a rusty / painted / poorly riveted or welded panle and some of your vehicle wireing then it will choose the wires every time. A lot of current traveling through small wires or even jumping across incredible small distances within some electronic components means trouble either now or in the future. Be aware that even if the current does not actually break over inside some electronic components it can (and does) 'stress' the small devices leading to a shortened service life. As has already been mentioned above, get a good clean earth as close to your work as possible and disconect the battery. The only 100% sure method of damageing electronics is to unplug them and remove them from the vehicle. That's almost impossible and most people do not have any problems if they carry out the above suggestions.

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Follow Up By: Member - Chris R (NSW) - Wednesday, Jun 28, 2006 at 20:16

Wednesday, Jun 28, 2006 at 20:16

Thanks for that. At this stage very little to remove. But once the studs get welded into the cabin I'll be installing HF UHF and dare I say... MP3... (subject for another day - or is it already solved with simple solution)

regards

Chris

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Reply By: Member - MrBitchi (QLD) - Wednesday, Jun 28, 2006 at 07:50

Wednesday, Jun 28, 2006 at 07:50

The issue is with voltage spikes frying the computer. Most places that regularly do welding on cars, ie exhaust shops, these days hook a diode pack across the battery to suppress spikes without disconnecting the battery. If you don't have a suitable suppressor then disconnect the battery. Shops don't disconnect as it means they then have to reprogram things like stereos etc. Also some vehicles lose their computer memory and have to be "retrained" (sounds like some co-workers i know;-) before the car will run again.

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Follow Up By: Member - Chris R (NSW) - Wednesday, Jun 28, 2006 at 20:24

Wednesday, Jun 28, 2006 at 20:24

Hi John

That last bit's a bit frightening " ..before the car will run again" I suspect the troopie hasn't learnt anything yet. Big messages out of all the replies is 1. really good earth very close to the electrode, 2. battery disconnect and 3. don't grow beard until the jobs done.

Thanks for advice

Chris

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Follow Up By: Member - MrBitchi (QLD) - Thursday, Jun 29, 2006 at 07:49

Thursday, Jun 29, 2006 at 07:49

Chris,
Comes from my own experience. Had some welding done on the towbar of the Paj and after having the battery disconnected for a couple of hours the car would start but no way would it idle without stalling. Had to go through a 'computer relearn' procedure to get it to run again. Not a problem if you know about it in advance and know how to do it but no repair shop would want to take the time involved if they could avoid it.

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Follow Up By: Member - Chris R (NSW) - Thursday, Jun 29, 2006 at 21:16

Thursday, Jun 29, 2006 at 21:16

Thanks John,

I took the risk today and applied all the advice with local welding shop. We tigged 4 studs into the cabin to support 2x 190cm shelves above the cargo area windows. (Part of a long fitout to own design prior to 6-24 (??) months continuous touring mountains beaches deserts)

We used the studs themselves as the earthing points - me supporting the clamp on the last couple of threads while the tigger tigged - very neat. Just one spark flew - and was a good reason to have two of us on hand.

Cheers
Chris

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Follow Up By: Member - MrBitchi (QLD) - Friday, Jun 30, 2006 at 07:32

Friday, Jun 30, 2006 at 07:32

"applied all the advice"
I assume you mean you disconnected your battery, in which case there is no risk.

"Just one spark flew"
You'll never see the one that causes the voltage spike that fries your computer......

Hope the rest of your fit out goes well.

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